Although the burden of stroke falls disproportionately on blacks, most of our information on stroke risk factors comes from studies in white populations only. This research plan details a set of interrelated subprojects aimed at a better understanding of the determinants of stroke in biracial populations. The proposal is based on five hypotheses: 1. The black-white difference in stroke mortality is due to a greater prevalence and severity of hypertension; 2. The black-white difference in stroke mortality is due primarily to a higher incidence of stroke among blacks rather than to a higher case-fatality rate; 3. Risk factors for stroke operate similarly in black and white populations but, because the distribution of risk factors differs between the races, the percentage of strokes associated with each risk factor differs between blacks and whites; 4. The differences in stroke subtypes and localization of cerebral atherosclerosis between blacks and whites is explainable by differences in the distribution of known risk factors. 5. Stroke in the young is not adequately explained by the distribution of established risk factors such as hypertension, diabetes and cardiac impairment. To test these hypotheses six subprojects are proposed. First, risk factors for stroke mortality will be studied in the screenees of the Multiple Risk Factor Intervention Trial. Second, risk factors for stroke incidence will be studied in the National Health and Nutrition Examination Survey Epidemiologic Followup Study. Third, racial differences in stroke case-fatality rates will be studied in the NINCDS Stroke Data Bank. Fourth, a case-control study of stroke in the biracial population of Baltimore will be developed focusing primarily on hypertension, lipoprotein abnormalities and glucose metabolism. Fifth, these same risk factors will be correlated with location and severity of angiographically defined cerebrovascular disease. In addition, the development of a population-based case ascertainment system for young strokes is proposed. This resource would be used to explore the reasons for the disproportionate stroke rate among young blacks, and to conduct case-control studies of less well established risk factors. These projects will contribute to the design of optimal stroke prevention strategies for all segmets of our population.